There is a long-standing problem concerning atmospheric pollution caused by emission of sulfur dioxide from industrial plants such as power plants and metallurgical smelters.
To accomplish the air pollution abatement, virtually all of the technology involves the scrubbing of the noxious gases with an aqueous media. While water alone as a scrubbing medium will remove particulate matter and sulfur dioxide, the presence of sulfur dioxide and other acidic materials such as other sulfur oxides and nitrogen oxides in the gases to be scrubbed necessitates the addition of a neutralizing substance such as lime, or any caustic or alkaline substance, to the aqueous scrubbing medium. The use of such chemical reagents in the aqueous scrubbing medium gives rise to the formation of chemical precipitates which, possibly augmented by particulate matter already present in the gas stream and aqueous scrubbing medium, cause deposits commonly known as "scale" to adhere to the internal surface of the gas scrubbing apparatus and such deposits may accumulate until the apparatus becomes clogged to an inoperable state and must be cleaned out.
Furthermore, most heretofore proposed and used gas scrubbers are in vertical stacks and have several consequent disadvantages. For example, the flow of the aqueous cleaning media through the stack is subject to the vagaries of gravitational influence because such solutions are fed from, at, or near the top of the stack and flow to the bottom. In many instances, there is inadequate retention time for the solution and insufficient contact between the downwardly flowing solution and upwardly flowing gas whereby the desired chemical reaction is not obtained. In addition the aqueous solution may be caught in the surge of the flowing gases and blown upwardly to the emission point which requires additional and expensive equipment to contain the aqueous solution within the stack and to clean the deposits.
Very little, if any, provision has been made in known scrubbers to effect an intimate contact or intermixing between the aqueous cleaning media and the noxious gases. These fluids are instead permitted to pass in a flow countercurrent to each other and do not attain the desired chemical reactions.